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42 AUSTRALIAN SKY & TELESCOPE JULY 2016

6633

IC 4756

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OPHIUCHUS

SERPENS

CAUDA

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M

anystargazersdon’tobserveexclusivelywitheitherbinoculars

oratelescope,butswitchbackandforthasneeded.There’sa

lottobesaidforexaminingthesameastronomicaltargetwith

different instruments.

IwasremindedofthiswhenIrevisitedNGC 6633,anopencluster

intheeasternreachesofOphiuchus.WhenIwasanewcomerto

astronomical sketching, this cluster was one of my first targets. Only

laterdidIlearnitsnickname:theItalyCluster.MicheleBortolotti

andGuidoRoccaofVerona,Italy,hadpointedoutthatNGC6633was

reminiscentoftheirhomecountry’sfamous‘boot’shape.BecauseI’d

usedareflector,mysketchwasinverted.WhenIturnedthedrawing

around,Italy’sshapewasnotjustobvious,itwasunavoidable.There’s

evenastellarSicilyanchoredonthe5th-magnitudeforegroundstar

HD 170200.

WhenIvisitedtheareaonapre-dawnbinocularhunt,Iwas

delightedtoseetheItalyshapeofNGC6633wasreadilyapparent

throughmy10×50binoculars.MaybeIshouldhaveanticipatedthat

—withamaximumextentofnearly1/2°and a magnitude of 4.6, the

clusterisbigandbrightenoughtoshowconsiderabledetailthrough

binoculars.Forachallenge,seehowmanystarsyoucanresolve.Ata

distance of 1,200 light-years, most of the cluster’s 150-plus members

mergeintoanebulousglow,leavingonlyadozenortwoofthe

brightest blazing in the foreground.

MostguidesincludeNGC6633inabandwithIC4665andIC4756.

ButIhaveotherhomeworkforyou:pickoutthestreamoffaintsuns,

about 1° wide, which runs north from NGC 6633 before breaking into

several chains of stars, like branches from the trunk of a tree, near the

border with Hercules. ✦

The stars of Italy

21

h

SAGITTA

AQUILA

CAPRICORNUS

PISCIS AUSTRIN

M30

57

Altair

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EN

WHEN

EarlyJune 10p.m.

Late June 9 p.m.

Early July 8 p.m.

Late July 7 p.m.

These are standard times.

HOW

Go outside within an hour or

soofatimelistedabove.Hold

themapoutinfrontofyou

andturnitaroundsothelabel

forthedirectionyou’refacing

(suchaswestornortheast)is

right-side up. The curved edge

represents the horizon, and the

starsaboveitonthemapnow

matchthestarsinfrontofyouin

thesky.Thecentreofthemapis

the zenith, the point in the sky

directly overhead.

FOR EXAMPLE: Turn the

mapsothelabel‘FacingNorth’

is right-side up. About halfway

fromtheretothemap’scentreis

thebrightstarArcturus.Goout

andlooknorthnearlyhalfway

from horizontal to straight up.

There’s Arcturus!

NOTE: The map is plotted for

35° south latitude (for example,

Sydney, Buenos Aires, Cape

Town). If you’re far north of there,

starsinthenorthernpartofthe

skywillbehigherandstarsinthe

south lower. Far south of 35° the

reverseistrue.

ONLINE

You can get a sky chart

customised for your

location at any time at

SkyandTelescope.com/skychart

USING THE

STAR CHART

Binocular Highlight

MATHEW

WEDEL

isapaleontologist

and associate

professor of

anatomybyday.

By night, he is

an “adventurous

stargazer” who

blogs at10minute

astronomy.

wordpress.com

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magnitudes

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